Touch screen is a touch sensing input device, which is widely used in cell phone, television and other media. According to touch sensing theories, touch screens can be divided into resistive touch screens, capacitive touch screens and so on. Since a resistive touch screen has low cost and is easily manufactured and controlled, it has been popular for many years. Recently, a capacitive touch screen, which has high light transmittance and extended life, and is anti abrasive and resistant to temperature variation and humidity of environment, and has the multi-point touch function, has received much attention in the industry.
To ensure a capacitive touch screen works efficiently, a transparent capacitive sensing array is desired. When a body or a special touch device, e.g., a stylus, approaches a capacitor induction electrode, capacitance detected by a sensing control circuit may be changed. According to capacitance variation in a touch region, touch situation in the touch region by the body or the special touch device can be recognized. According to formation methods of capacitors, conventional touch screens can be divided into self capacitive touch screens and mutual capacitive touch screens. For a self capacitive touch screen, variation of capacitance formed between a sense electrode and an alternating current ground or between a sense electrode and a direct current level electrode is taken as a touch sensing signal; for a mutual capacitive touch screen, variation of capacitance formed between two sense electrodes is taken as a touch sensing signal. In other conventional methods, touch situation can be recognized based on variation of charge amount in a touch region corresponding to the variation of capacitance.
However, for a capacitive touch screen, touch recognition based on detection of variation of charge amount can be easily influenced by using environment and touch manner of the touch screen. For example, when a device which can generate electric radiation (e.g., a cell phone or a hairdryer) is on operation near the touch screen, the charge amount on the surface of the touch screen will change abnormally. In this situation, if a conventional method is applied in touch recognition, a false recognition result may be obtained and even a misoperation may be caused. For another example, if the touch screen is touched by a finger with a slight strength and no effective touch contact is formed, a false recognition may be caused as well.
Therefore, a new technology which can perform touch recognition more accurately is desired.